The invention pertains to apparatus and method for three-dimensional display of three-dimensional objects and scenes.
In recent years, various attempts have been made to create three-dimensional displays for various applications, particularly three-dimensional television. Because of the inherent mathematical and practical complexities in the three-dimensional imaging problem, as well as the ad hoc nature of previous approaches, the degree of success thus far has been rather limited.
Most developments in three-dimensional display systems have been primarily in stereoscopic techniques, and incorporating a set of discrete multiviews of the three dimensional scenes. These have included both binocular parallax and autostereoscopic three-dimensional systems. Stereoscopic techniques typically require the observer to use a viewing device. In contrast autostereoscopic techniques, which include for example, holographic, lenticular screens and parallax barriers, produce three-dimensional appearance without the use of any special viewing device. The article by Motoki, Isono and Yuyama, in the Proceedings of the IEEE, Vol 83, No. 7, July, 1995, pp. 1009-1021, provides a convenient summary of the present state of the art of three-dimensional television, one of the major applications of three-dimensional display systems. As of yet, there is not a practical system which may be considered to offer all of the capabilities necessary to achieve widespread success.
Nomura et al., in U.S. Pat. No. 5,493,427 disclosed apparatus for three-dimensional display using a liquid crystal panel. The inventors' technique relies on simultaneously displaying a plurality of distinct parallax images using a lens with a variable optical characteristic attached to the liquid crystal panel. An alternative embodiment incorporates a head detecting section for detecting a spatial position of an observer's head, and a control section connected to the head detecting section for controlling an operation of the optical characteristic variable lens based on position information of the observer's head.
An autostereoscopic display system is disclosed by Woodgate et al. in U.S. Pat. No. 5,465,175. The device utilizes two lenticular screens and a plurality of light sources which produce divergent light beams for displaying two interlaced views, thereby producing an autostereoscopic image. Another autostereoscopic display system is described by Eichenlaub in U.S. Pat. No. 5,457,574. The inventor discloses a display having an optical system and one or more light sources which provide high brightness of the observed three-dimensional images and a high brightness-to-input power ratio. This is achieved by having the light pass directly through the optical system directed to the observer's eyes, instead of being diffused across the field of view.
Kurata et al. in U.S. Pat. No. 5,408,264, disclose a three-dimensional image display apparatus for optically synthesizing images formed on different surfaces on a display screen. In their invention, a plurality of display devices is used with a first and second optical means to synthesize a plurality of images formed at different positions. In a preferred embodiment, the first optical means has polarizing characteristics. In U.S. Pat. No. 5,497,189, Aritake et al., disclose a stereoscopic display apparatus which is capable of displaying sequentially a plurality of 2-dimensional images of different visual directions.
Powell in U.S. Pat. No. 5,483,254 discloses a device for forming and displaying stereoscopic images. The display is comprised of a non-planar upper substrate having a series of alternating raised and depressed regions and a non-planar lower substrate having a shape corresponding to the upper substrate, with an electrically controllable light transmissive material contained within the two substrates. The 3D video display device operates thereby to form and displace stereoscopic images at predetermined viewing angles.
A system for displaying three dimensional video is disclosed by Carbery in U.S. Pat. No. 5,475,419. This invention uses a dual-lensed video camera to generate signals representing a subject from each of two different perspectives. The signals are spliced to form a combined video signal consisting of an alternating series of fields representing the image from two perspectives. The video signal is then sent to a receiver including a video screen equipped with a refracticular surface, thereby producing a stereoscopic image towards the eyes of a viewer.
Thompson et al., in U.S. Pat. No. 5,446,479 disclose a multidimensional array video processor system. The system consists of a processor and a video memory. The processor converts a stream of digital information to extract planes of a three dimensional image to store into the video memory to display a three dimensional image. A spatial light modulator is connected to the video memory to receive and display a plane of said image to display a three dimensional image.
Kuga, in U.S. Pat. No. 5,592,215 discloses a stereoscopic picture system which uses multiple display panels having three-dimensionally arranged pixels to produce a stereoscopic picture. The invention utilizes a simple coordinate transformation to produce the picture on the three-dimensional display.
Zellitt, in U.S. Pat. No. 5,790,086 discloses a 3-D imaging system in which the apparent distance of a pixel of the image is varied, on a pixel by pixel basis. This variation in perceived distance is achieved using specially constructed optical elements aligned with the pixels of the image. The optical elements are formed such that the focal length of each element varies across the surface of the optical element, which allows the perception of different depths to be realized.
The most advanced system for display of three-dimensional scenes is based on holography, but a practical realization is many years in the future. A review of this approach may be found in the article by Benton, in the Proc. TAO 1st Int. Symp. on 3D Image Communication Tech., 1993, pp. S-3-1-1-S-3-1-6. Wakai et al. in U.S. Pat. No. 5,430,560 disclose a holographic image display system. The system incorporates a coherent light source and a hologram having a plurality of divided areas, which are sequentially irradiated by the light source to thereby produce the three-dimensional image signal.
The prior art, exemplified by the references that have been briefly discussed, has focussed primarily either on stereoscopic techniques with the use of polarizing or shutter glasses, or relatively primitive autostereoscopic display systems. A major shortcoming of the prior art is its reliance on stereoscopic imaging techniques, in which a set of distinct perspective or parallax views are projected to the viewer in essentially an ad hoc fashion, with no direct correspondence to the radiance of the original three-dimensional scene. This has led to the production of relatively poor three-dimensional display systems. A true multiviewpoint autostereoscopic system which can offer practical, cost effective, as well as realistic and aesthetically acceptable images from a continuum of viewpoints has not yet been developed.